This weeks' NEJM has an article about the sudden uptick in SAEs for the Heartmate device:
The occurrence of confirmed pump thrombosis increased steeply after approximately March 2011, from 2.2% (95% confidence interval [CI], 1.5 to 3.4) at 3 months after implantation to 8.4% (95% CI, 5.0 to 13.9) by January 2013